Olympian and orthopedic surgeon Eric Heiden tells you how to get more bang for your bike ride.
Many fitness programs promote the idea that you lose weight simply because you burn a certain number of calories while you're exercising. But you also continue to burn calories after you exercise. We call this phenomenon exercise after-burn.
For the Tour de France riders we've all been watching, exercise after-burn can last overnight or for days. Exercise after-burn utilizes additional calories by performing the processes necessary to return your body to its pre-exercise state. These calories are used to:
* Replenish your glycogen (the way you store fuel in your muscles and liver) and oxygen stores.
* Resynthesize phosphagen (ATP-PC).
* Remove lactate.
* Repair the wear and tear on your muscles caused by exercise (and these patch kits are made up of protein, which is costly in terms of calories).
* Return your increased ventilation, blood circulation and body temperature to pre-exercise levels.
* Produce the hormones exercise induces (which also require protein).
Basically, the greater the intensity and duration of your exercise, the longer the after-burn. You may no longer be moving, but internally your chemical processes and enzymatic activity are still churning away. If one of your exercise goals is weight loss, you should be aware that there is a substantial body of research that hints at how exercise after-burn might be maximized.
Aerobic exercise causes significant exercise after-burn, research concludes—the longer the session, the better. When subjects exercised at the same intensity but for different lengths of time, those who exercised for 20 minutes subsequently burned 55.5 calories during after-burn. Those who exercised for 40 minutes burned 73.5 calories during after-burn, and those who went 60 minutes burned 159.5 calories during after-burn.
Likewise, the higher your exercise intensity, the greater the magnitude and duration of after-burn—and the higher the additional caloric expenditure—you will experience. Following sessions of high-intensity aerobic exercise, for example, your after-burn might last 10 hours; lower-intensity efforts might wrap up after just 3 hours; the lowest efforts elicit as little as 20 minutes of after-burn. Researchers measured the total calories expended by two groups: one that exercised at low intensity long enough to burn 500 calories, and another that exercised at high intensity long enough to burn 500 calories. Both consumed precisely 500 calories during exercise, but the high-intensity exercise consumed significantly more in after-burn—an additional 45 calories to be exact—while the low-intensity exercise stimulated after-burn that consumed only 24 more calories.
Several studies have also concluded that intermittent exercise elicits greater after-burn than continuous exercise. In one study, the after-burn of a continuous run of 30 minutes at 70 percent VO2 max was pitted against that of a run consisting of 20 bouts of 1-minute duration at 105 percent VO2 max (referred to as supramaximal exercise). The latter disposed of more than twice as many calories—75 calories (versus 34.5 calories burned after the continuous run). When subjects performed exercise of the same intensity for the same number of minutes, researchers observed that runners whose exercise had been split into separate sessions (in this case, two 25-minute runs versus one 50-minute run), again the intermittent exercise imparted double the caloric after-burn.
Other factors that seem to influence after-burn include gender. An investigation comparing male and female subjects reported a more significant after-burn in men. After 30 minutes of the highest-intensity exercise, females burned an average of 121.5 calories, while men doing the same exercise averaged 140.5 calories in after-burn.
